Researchers at IBM have mathematically proven that there are certain functions restricted classical computers cannot perform but restricted quantum computers can. However, they concede that quantum computers can’t defeat their classical counterparts merely on the basis of a different architecture. Not only is there a need for finding and writing theoretical proofs of the advantages the quantum computers offer but also demonstrate them experimentally, they said.   

In the paper titled, “Quantum advantage for computations with limited space,” published in Nature Physics, researchers said that for the first time, they demonstrated that qubits offer more value than bits as a medium of storage during computations. “Through our research, we’re exploring a very simple question: how does the computational power differ when a computer has access to classical scratch space versus quantum scratch space?” the IBM team said.

The researchers called their experiment “the limited space computations” that involved circuits restricted to using two-input gates and a single bit of computational/ scrap space. This restriction was put in place to ensure that a fair comparison was established between the quantum and classical computational space, researchers said, adding that they didn’t keep the experiment limited to just theoretical proofs and, therefore, a real quantum computer was involved to go head to head with its classical counterpart. The classical one’s computational capacities were also increased by giving it access to random Boolean gates.

“But even with access to this randomness, the classical computer can only succeed 87.5 percent time whereas a perfect, noiseless quantum computer could succeed 100 percent time,” researchers said.

They said the conclusions in their paper had other important implications too. To start with, it showed even the present-day noisy computers are powerful computational tools. Physicist Alexander Holevo’s work explained how one qubit could only store one bit of information, but the IBM team seemed to have broken this boundary by demonstrating that they could store much more than one bit as the intermediate results of a computation.

Researchers further said that the IBM quantum team is continuing to develop hardware that they hope will speed up solving some of today’s hardest quantum computing problems.

And while this is on, the theory team will continue the equally important work of investigating and demonstrating the uniqueness of quantum computation, and finding the benefits over classical computers such uniqueness may deliver.